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arch dam[′ärch ‚dam]
a curved dam whose strength comes from its construction as an arch, with the horizontal pressure of the water transmitted almost entirely to the shore or abutments.
Arch dams are generally made from concrete when there is a strong (rocky) base and rocky shores. The dam may be fixed (that is, without spillways) or effluent. Depending on the ratio of the surface thickness of the dam b to its height h, the dams are subdivided into arch dams proper (B/H0.35) and gravityarch dams (b/h = 0.36–0.6). The thickness of an arch dam depends on the form of the cross section of the valley in the range of the dam (the most desirable form is near-triangular, the least desirable is rectangular) and on the ratio of the width of the valley (B) at the level of the dam’s crest to the height of the dam (B/h). This ratio is generally 0.5–3.5 (in certain cases it reaches 8 and higher).
Modern trends in the construction of arch dams include a decrease in the thickness of the dam and an increase in stress in the concrete, lightening of the load on the dam by the installation of a joint around the perimeter of the valley, and the use of spillway openings. Arch dams, owing to their structural advantages, reliability, and economy, have been widely used in mountain rivers with rocky channels; they have been built as high as 270 m (the Inguri Hydroelectric Power Plant in the Georgian SSR).
REFERENCESGrishin, M. M. Gidrotekhnicheskié sooruzheniia. Moscow, 1962. Spravochnik po gidrotekhnike. Moscow, 1955.
A. R. BEREZINSKII